Grinding the beans yourself does make for better coffee, I think. Having said that, it also depends on how much coffee you drink and whether or not the ground beans that you buy are freshly ground. So if you go to, say, a specialist tea and coffee shop that grinds the beans to order, and if you drink sufficient coffee at home to get through what you buy quickly (within a week, for example), then the difference is probably not so great as it would be if you buy pre-ground beans from a supermarket and don't use the coffee for a month or more...